JPS61107534A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To form a magnetic recording medium with which a high output and high S/N are obtd. and which has excellent heat resistance, durability, still image stability, etc. by incorporating polycarbonate polyurethane and specific compd. into a magnetic layer. CONSTITUTION:The polycarbonate polyurethane and the compd. expressed by the formula 1 are incorporated into the magnetic layer. Since the polycarbonate polyurethane is used as the binder resin for the magnetic layer, the wear resistance intrinsic to the urethane resin is provided; in addition the heat resistance is improved by the presence of the carbonate component. The running stability owing to the decreased coefft. of friction is obtd. and the solubility in a solvent is improved, by which the urethane concn. can be increased to increase film strength. No substituents are incorporated into the phenyl group existing in the molecule of the compd. expressed by the formula 1 and therefore the durability (more particularly still durability), heat resistance, etc. of the magnetic layer are improved and the high output and high S/N are obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to magnetic recording media such as magnetic tapes, magnetic sheets, and magnetic disks.

BACKGROUND OF THE INVENTION Generally, magnetic recording media such as magnetic tapes are manufactured by applying a magnetic paint made of magnetic powder, binder resin, etc. onto a support and drying it.

In such magnetic recording media, urethane resin is generally used as a binder resin for magnetic layers and the like. Conventionally known urethane resins are synthesized from polymeric diols, diisocyanates, chain extenders, and crosslinking agents (used as necessary).

Examples of polymeric diols include polyester diols obtained from adipic acid, butanediol, etc., polyether diols, and polycarbonate diols, and diphenylmethane diisocyanate and the like can be used as diisocyanates.

Further, the chain extender may be ethylene glycol, butanediol, etc., and the crosslinking agent may be polyols, polyamines, etc.

However, although such general urethane resin has excellent flexibility, it lacks hardness, resulting in poor mechanical strength of magnetic recording media against sliding contact with guide pins, magnetic heads, etc. Moreover, there are problems in terms of runnability and powder shedding. For example, when a polyester type urethane resin, polyvinylidene chloride, or vinyl chloride-vinyl acetate copolymer is used, there are problems particularly in heat resistance and still image stability.

On the other hand, in magnetic recording media, it has been known for a long time to add lecithin (based on natural phosphate esters and containing several percent of various higher fatty acids) as a dispersant to magnetic paints.

However, when lecithin is added, satisfactory results cannot be obtained with the use of finely divided magnetic powder as a medium, and the calender roll is easily stained during calendering.

With the development of recent magnetic recording media, when urethane resin or lecithin, which is merely soft, is included in the magnetic layer, it is necessary to improve the durability of the medium during running, the stability of still images, and the quality of fine magnetic powder. Dispersibility etc. are insufficient.

As a modified version of the above-mentioned polyurethane,
A polyester polyurethane disclosed in Japanese Patent No. 6-137522 is known, but when this is used as a binder, the ester component improves heat resistance, but solvent solubility decreases and the urethane concentration cannot be increased too much. This will reduce the film strength. For this reason, when a lubricant is used in combination, the amount of lubricant must be increased in order to control the lubricity of the entire binder and maintain film strength.
This is unsuitable because blooming occurs due to the large amount of low-molecular-weight lubricant.

Furthermore, phosphate ester surfactants used in magnetic recording media are disclosed, for example, in Japanese Patent Publication No. 47-26882. Among phosphoric esters, those well known in the field of magnetic recording media include phosphoric esters of compounds in which ethylene oxide is added to aliphatic alcohols or alkylphenols, which are used as dispersants. This is often expressed by the following equation (-■).

0 ・R-0÷CHzCHzO+7P-OH...' (
1) ■ (However, X is a hydroxyl group or a group represented by RO+CHz CHz Oto, R is an alkyl group, alkenyl group, or alkylphenyl group.) Magnetic recording using a phosphate ester represented by this formula (I) For example, the medium is
It is described in Japanese Patent Publication No. 9-21087, Japanese Patent Application Laid-Open No. 53-15803, and Japanese Patent Publication No. 57-44970.

The present inventor conducted various studies on such known phosphoric acid esters, and as a result, discovered that they had the following problems. That is, in recent years, as the demand for high-density recording has increased and magnetic powder has become finer, the phosphoric acid ester of formula (I) used in conventional magnetic recording media has been
It was found that the /N ratio could not be improved sufficiently. That is, especially for video systems such as VH3 and Beta systems, higher-density 8mm video, high-definition video, electronic still recording, high-density sheet recording, etc., even if conventional phosphate esters are added to the magnetic layer, Only insufficient magnetic recording and reproducing characteristics can be obtained.

OBJECT OF THE INVENTION An object of the present invention is to provide a magnetic recording medium that can obtain high output and high S/N ratio, and has excellent heat resistance, durability, still image stability, etc.

20 Structure and Effects of the Invention The magnetic recording medium according to the present invention is a magnetic recording medium in which a magnetic layer contains polycarbonate-based polyurethane and a compound represented by the following general formula.

General formula: (However, A is a hydroxyl group or 10M (M is an alkali group, and n is a real number from 1 to 30.) According to the present invention, polycarbonate polyurethane is used as the binder resin of the magnetic layer. Therefore, in addition to exhibiting the abrasion resistance characteristic of urethane resins, the presence of the carbonate component improves heat resistance (Tg), provides running stability by reducing the coefficient of friction, and improves solubility in solvents. As a result, the film strength can be increased by increasing the urethane concentration.In this case, it is desirable that there are no ester bonds in the polyurethane molecules; Since there is no change over time due to hydrolysis, the layer does not get scratched or peeled off, and smooth running properties can be maintained.However, the heat resistance is sufficiently improved by containing the ester component. What is meant by the above "ester bond" is, in particular, a bond formed by the reaction between a normal carboxylic acid and an alcohol, and is (usually) a bond that is adjacent to the carbon atom forming the carbonyl bond. Refers to those in which carbon atoms are directly bonded.

-NHCOO- (urethane bond) and -〇-C-O- (carbonate bond) are the ester bonds 1
shall not be included.

In addition, the above-mentioned polycarbonate-based polyurethane has good compatibility with other polymers (e.g., vinyl chloride-vinyl acetate copolymer, nitrocellulose) used in combination to improve film strength and dispersibility of magnetic powder, etc., so it improves film physical properties. is less likely to fluctuate, and the resulting medium has good runnability. In addition, by adjusting the amount of isocyanate (described later) and adding polyols other than polycarbonate polyol (described later), it is possible to correct the curl of the medium and prevent disturbances (skew) in the reproduced screen.
Alternatively, still characteristics can be improved.

Further, in the process of arriving at the present invention, the inventors obtained the following new knowledge. Conventional phosphoric acid esters, especially aromatic phosphoric acid esters of the above-mentioned formula (I), are used exclusively as dispersants from the viewpoint of improving the dispersibility of magnetic powder.
The phenyl group in the molecule is substituted with an alkyl group to form an alkylphenyl group. Therefore, there has been a strong preconception that the phenyl group has poor dispersibility unless it has a substituent such as an alkyl group. However, upon investigation by the inventor, the above-mentioned
“The dispersibility is determined only by the physical properties of the phosphate ester itself, and when it is actually added to the magnetic layer, it depends on the compatibility with the various components of the magnetic layer and the phosphate ester molecules in the magnetic paint. No consideration has been given to the behavior of
Because the substituted alkyl group of the alkylphenyl group present in the molecule causes steric hindrance or undergoes a certain movement, compatibility with other components in the magnetic layer becomes poor, and the durability of the magnetic layer decreases. considered to be a thing.

On the other hand, the compound of the present invention having the above general formula (hereinafter referred to as the "compound of the present invention") has no substituents introduced into the phenyl group present in the molecule, so the above-mentioned phenomenon occurs. It is possible to improve the durability (especially still durability), heat resistance, etc. of the magnetic layer while sufficiently maintaining its own dispersibility, and to obtain high output and high S/N ratio. In this case, the phenyl group in the molecule has lipophilicity and rigidity (r
igid) and exhibits hydrophobicity, while the ethylene glycol residue (-(-cH2CH20+-) within the molecule exhibits hydrophilicity. By adjusting the ratio of these two groups, an appropriate HL B (Hydrophilic-
L 1pophilicB alanca: Parental tree-
lipophilic balance).

In the compound of the present invention, in the above general formula, n should be a real number of 1 to 30 in order to maintain the dispersibility of the magnetic powder in the magnetic layer, and if n = 2 to 20, the dispersion will be further improved. The properties become better. Further, when A is 00→CHICH+Oh, it becomes a diester, but when used in combination with a monoester in which A is a hydroxyl group, a medium with preferable characteristics can be obtained. Of course, the monoester and the diester may be used alone. In addition, as A in the above general formula, -0Na, -OK
In this case, it is preferable to pre-treat the magnetic powder with the compound of the present invention before adding it to the paint.

Further, in the compound of the present invention, it is desirable to set the HLB of the compound to 8 to 14 by selecting n in the above general formula. That is, if the HLB is smaller than 8, the lipophilic property becomes strong, and if the HLB is larger than 14, the hydrophilic property becomes strong. be.

The amount of the compound of the present invention added to the magnetic layer has an appropriate range, and is preferably 1 to 10 parts by weight, more preferably 2 to 7 parts by weight, based on 100 parts by weight of the magnetic powder. By adding 1 part by weight or more, the dispersibility, durability, etc. are sufficient and the surface properties of the layer are improved, and by adding 10 parts by weight or less, the viscosity of the paint is sufficient and the film thickness can be controlled. It becomes easier.

Specific examples of the compounds of the present invention are as follows, but are not limited thereto.

and/or this monophosphate ester exemplified compound ■ OH and/or this silicate ester exemplified compound ■ and/or this silicate ester exemplified compound ■ and/or this silicate ester exemplified compound ■ OH and/or this silicate ester exemplified compound
□゛Exemplary Compound■ Exemplary Compound■ Exemplary Compound■ and/or its silicic acid ester Next, the structure of the above-mentioned polycarbonate-based polyurethane used as the pine resin of the magnetic layer of the magnetic recording medium of the present invention will be explained. This polyurethane is, for example, polycarbonate polyol [H→0-R-0-
It is synthesized by a urethanization reaction between C-0-)yR-OH) and a polyvalent isocyanate (for example, 0CN-R'-NCO).

H-+O-ROCO+rR-OH+OCN-(However, R
, R' is an aliphatic or aromatic hydrocarbon group. l is preferably 50 or less to reduce Tg and prevent stickiness.
1 to 30 is desirable. m is 5 to 500 in order to maintain film forming ability and improve solvent solubility, and 10 to 300.
is desirable. l and m are selected so that the average molecular weight of this polycarbonate polyol polyurethane is preferably 50,000 to 200,000. ) The polycarbonate polyol that can be used here is formed by linking polyols with carbonate bonds, and is obtained, for example, by condensation of a conventionally known polyhydric alcohol with phosgene, chloroformic acid ester, dialkyl carbonate, diallyl carbonate, etc. .

Examples of the polyhydric alcohol include 1.10-decanediol, 1.6-hexanediol, 1.4-butanediol, 1,3-butanediol, neopentyl glycol, 1.5-bentanediol, and the like. The number of carbon atoms in this polyhydric alcohol, such as diol, is important and is preferably set to 4 to 12;
This is because, as shown in the figure, powder drop-off (after running 100 times) is likely to occur in both cases where the number of carbon atoms is 4 and 12. Correspondingly, the molecular weight of the polycarbonate polyol is as shown in Figure 2 (powder falling off after 100 runs = 60°C, 1
(after storage for a week) to approximately 700 to 3,000.

In the above-described urethanization reaction, it is important that active hydrogen (due to -〇H) exists in the polycarbonate, but in addition to the polyhydric alcohols listed above as compounds that supply similar active hydrogen, Ethylene glycol, diethylene glycol, propylene glycol, 1.4-7" ethylene glycol, bisphenol A1
Glycerin, 1,3,6-hexanediol, trimethylolpropane, pentaerythritol, sorbitol, sucrose, dipropylene glycol, methyljetanolamine, ethylbiisopropanolamine, triethanolamine, ethylenediamine, hexamethylenediamine, bis(p -aminocyclohexane), tolylenediamine, diphenylmethanediamine, methylenebis(2-chloroaniline), and/or these compounds, ethylene oxide, propylene oxide, butylene oxide, tetrahydrofuran, styrene oxide, etc. (hereinafter simply alkyl,
7. Oyakei, abbreviated as 4. ), yo. seed
; Examples include polyether polyols obtained by adding the above.

Next, although the active hydrogen-containing polycarbonate such as the above-mentioned polycarbonate polyol can be used alone, other polyhydric alcohols may be used in combination with the above-mentioned urethanization, and other known chain extenders may be used in combination. For example, when other low-molecular-weight polyhydric alcohols such as hexanediol and butanediol are used together, it can be expected that they will react with an excess amount of the polyisocyanate and promote gelation, but as shown in Figure 3, polycarbonate It is desirable to maintain the proportion of polyol at 80% or more in order to obtain sufficient wear resistance.

Next, the above polyvalent isocyanate is preferably an aromatic isocyanate, such as tolylene diisocyanate (TDI) (2,4-TD I, 2,6-
TDI), 2,4-tolylene diisocyanate dimer, 4,4'-diphenylmethane diisocyanate (MD
I), xylylene diisocyanate (XDI), meta-xylylene diisocyanate (MXDI), naphthylene-
Examples include 1゜5-diisocyanate (NDI), O-)lylene diisocyanate (TODI), and adducts of these isocyanates with active hydrogen compounds, and those with an average molecular weight in the range of 100 to 3.000 are preferable. be. Specifically, Sumidur T80, Sumidur 44S1 PF, L1 Desmodur T65, Sumidur 15, R1 RF, IL, and SL manufactured by Sumitomo Bayer Urethane Co., Ltd.; products manufactured by Takeda Pharmaceutical Company; Famous Takene) 30
0 S, 500; Product rNDI manufactured by Mitsui Nisso Urethane Co., Ltd.
J, rTODI: Nippon Polyurethane Co., Ltd. products Desmodur T 100, Millionate MR, Same MT, Coronate L; Kasei Upjohn Co. products PAP I-135
, TD I65, 80. 100, isocyanate 1
Examples include 25M and 143L.

On the other hand, examples of aliphatic isocyanates include hexamethylene diisocyanate (HMD I), lysine isocyanate, and trimethylhexamethylene diisocyanate (HMD I).
THDI) and adducts of these isocyanates and active hydrogen compounds. Among these aliphatic isocyanates and adducts of these isocyanates and active hydrogen compounds, those with a molecular weight of 10 are preferable.
It ranges from 0 to 3,000. Among the aliphatic isocyanates, non-alicyclic isocyanates and adducts of these compounds with active hydrogen compounds are preferred.

Specifically, for example, Sumidur N1 Desmodur Z 4273 manufactured by Sumidur Urethane Co., Ltd., Duranate 50M, 24A-100, and 24A manufactured by Asahi Kasei Co., Ltd.
-90CX, Coronate HL manufactured by Nippon Polyurethane Co., Ltd., and TMD I manufactured by Huls.

In addition, examples of alicyclic incyanates among aliphatic isocyanates include methylcyclohexane-2,4-
Examples include diisocyanate, 4,4-methylenebis(cyclohexyl isocyanate), isophorone diisocyanate, and adducts of active hydrogen compounds thereof. Specifically, the product rI PD 14 manufactured by Huls Chemical Co., Ltd.
, rIPDI-T1890J, same-H2921, same-
B 1065, etc.

Examples of other polyvalent isocyanates include adducts of diisocyanates and trivalent polyols, and pentamer 1 of diisocyanates. Examples of these are an adduct of 3 moles of tolylene diisocyanate and 1 mole of trimethylolpropane, an adduct of 3 moles of metaxylylene diisocyanate and 1 mole of trimethylolpropane, and tolylene diisocyanate.

Among the polyvalent isocyanates mentioned above, the aromatic ones act as hard components (hard segments), so
Polycarbonate (polyol) is desirable because it can sufficiently exhibit the rigidity of polyurethane.

Figure 4 shows the change in adhesiveness depending on the average molecular weight of the same polyurethane.If the average molecular weight is set in the range of 50,000 to 200,000, the adhesiveness can be kept low, but in this case,
If an aromatic isocyanate is used as the isocyanate component of the above polyurethane, the still durability can be sufficiently increased as shown by curve a, but if an aliphatic isocyanate is used, the still durability becomes low as shown in the curve. I understand.

Among the aromatic isocyanates mentioned above, naphthylene-1
, 5-diisocyanate and diphenylmethane diisocyanate are particularly preferred.

The amount of isocyanate used above is such that the NCO groups (isocyanate groups) contained in the polyisocyanate are active hydrogen-containing compounds (e.g. polycarbonate polyol).
It is desirable that the equivalent ratio be 0.8 to 1.2, more preferably 0.85 to 1.1 with respect to the total amount of active hydrogen contained in the active hydrogen.

When producing the polyurethane according to the present invention, the following solvents may be used as necessary.

Amides such as dimethylformamide and dimethylacetamide, sulfoxides such as dimethyl sulfoxide, cyclic ethers such as dioxane and tetrahydrofuran, cyclic ketones such as cyclohexanone, acyclic ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone, cellosolve, 'butyl cellosolve,
Glycol ethers known as “carpitol”, ``butyl carpitol'', etc., acetic acid known as trade names ``cellosolve acetate'', ``butyl cellosolve acetate'', ``carpitol acetate'', ``butyl carpitol acetate'', etc. One or more types of glycol ether type solvents and dibasic acid ester type solvents known, for example, under the trade name "Gui Glyme";
Furthermore, the above solvents and esters such as ethyl acetate and butyl acetate, aromatic hydrocarbons such as benzene, toluene and xylene, methylene chloride, trichloroethylene,
Chlorine-based products such as trichloroethane and perchlorethylene,
Mixed solvents with alcoholic solvents such as methanol, ethanol, isopropanol, butanol, etc. In addition, 2,2,4-)dimethyl 1,3-bentanediol monoisobutyrate (Kyowanol M: Kyowa Hakko Co., Ltd.)
) can also be used as a solvent.

In order to produce the polyurethane according to the present invention, first, in a nitrogen atmosphere, for example, a polymer polyol and an isocyanate are mixed together in the presence of a catalyst and/or a solvent as necessary.
A prepolymer is produced by heating and reacting at 0°C to 100°C for several hours. The reaction is further heated at the same temperature for several hours to obtain a polyurethane resin according to the present invention. If necessary, a reaction terminator can be added and the reaction can be carried out by heating. Further, a solvent is appropriately added to reduce the viscosity at each stage of the reaction. The obtained polyurethane resin solution according to the present invention has a solid content of 15 to 60% and a viscosity of 200 to 70.0 OOcps/25°C.

As explained in Figure 4, it is desirable to select the average molecular weight of the polycarbonate polyurethane synthesized as described above in the range of 50,000 to 200,000. It has been confirmed that the surface properties of the magnetic layer also improve.

The layer containing the above-described compound of the present invention and polycarbonate polyurethane is configured, for example, as a magnetic layer 12 on a support 11, as shown in FIG. A back coat layer (BC layer) 13 is provided on the back surface of the support 11 to improve the winding appearance and running stability during tape winding.

Further, a urethane resin having a yield point may be used in combination with the above polycarbonate polyurethane. In other words, this urethane resin has a yield point YP as shown in the curve a in FIG. Up to YP, the elongation is very small even when stress is applied, which gives the urethane resin appropriate hardness, and after the yield point YP it shows the property of elongating with stress without breaking. It also has appropriate flexibility and binding strength as a binder resin. As a result, the mechanical strength of the magnetic recording medium is improved, damage such as wear during sliding contact, powder falling, etc. are significantly reduced, and running properties are also significantly improved. In particular, the magnetic tape for (1) TR has no edge bending, and the control track near the edge can be maintained and its function can be performed satisfactorily. The above yield point YP is important for the performance of urethane resin, and is 50 to 600 kg/co! , preferably 1
Desirably, there is a yield point in the stress range of 0.00 to 560 kg/ad (approximately 290 kg/cal in the example of FIG. 1). The range where the yield point exists is a stress of 50 kg/a + I
If it is above 600, it will prevent the resin from becoming too soft.
If it is less than kg/ant, it is possible to prevent the resin from becoming hard and brittle. Further, the urethane resin having this yield point has good dispersibility and improves the durability of the magnetic layer.

In order to exhibit the above-mentioned excellent performance, the urethane resin having a yield point preferably has a cyclic hydrocarbon residue in the molecule. The cyclic hydrocarbon residue is preferably a saturated cyclic hydrocarbon residue, including divalent or monovalent cyclic hydrocarbon residues.
cyclopentyl group, cyclohexyl group, etc., or derivatives thereof (for example, alkyl group substituted products such as methyl group,
Examples include those consisting of a halogen substituted product such as a chlorine atom. These saturated cyclic hydrocarbon residues are desirable from the viewpoint of imparting appropriate hardness to the urethane resin and availability of raw materials. Further, the bonding position of this cyclic hydrocarbon residue is preferably in the main chain of the urethane resin molecule, but it may be bonded to the side chain thereof. In addition, by changing the amount of components having cyclic hydrocarbon residues in the urethane resin, it is possible to obtain a urethane resin with any glass transition point (Tg), and the Tg can range from 0°C to 100
t, preferably θ°C to 90°C. If Tg is -30°C or higher, the resin becomes soft (T g <-30°C)
In addition, by setting the temperature to 100° C. or lower, it is possible to prevent the film from becoming unduly hard and brittle.

Urethane resins having this yield point can be synthesized by reacting polyols with polyisocyanates. At this time, in order to introduce the above-mentioned cyclic hydrocarbon residue, the following (1) to
Method (4) can be adopted.

(1) A method in which a polyhydric alcohol having a cyclic hydrocarbon residue in advance is used as a raw material for a polyol (for example, a polymeric diol).

(2) A method in which a dicarboxylic acid having a cyclic hydrocarbon residue in advance is used as an organic dibasic acid (dicarboxylic acid) serving as a raw material for the polyol.

(3) A method in which the polyhydric alcohol and dicarboxylic acid of (1) and (2) above are used as raw materials for polyol.

(4) A method of using a polyhydric alcohol having a cyclic hydrocarbon residue in advance as a chain extender, in combination with any of the above (1) to (3), or alone.

For example, the synthesis method for obtaining the above urethane resin is HO
OC(CHz) 4 COOH) or other diols such as butane-1,4-diol.

As the above-mentioned polyhydric alcohol which may have a cyclic hydrocarbon residue in advance, those having a cyclohexyl group in the molecular chain of the ethylene glycol structure can be used as described above, but in addition to such a structure, propylene glycol, butylene Glycols such as glycol and diethylene glycol, polyhydric alcohols such as trimethylolpropane, hexanetriol, glycerin, trimethylolethane, and pentaerythritol, or these glycols, or those having a cyclic hydrocarbon residue in their structure are used. can. Further, dibasic acids that can be used include phthalic acid, unitized sulfuric acid, maleic acid, etc., or those having a cyclic hydrocarbon residue in their molecules. Instead of the above polyol, S
-caprolactam, α-methyl-1-caprolactam,
Lactone polyester polyols synthesized from lactams such as S-methyl-3-caprolactam and T-butyrolactam; or polyether polyols synthesized from ethylene oxide, butylene oxide, etc. may also be used.

These polyols are produced by reacting tolylene diisocyanate with an isocyanate compound such as hexamethylene diisocyanate, methylene diisocyanate, or metaxylylene diisocyanate, thereby synthesizing urethanized polyester polyurethane or polyether polyurethane.

These urethane resins from the bottle are usually mainly made of
Produced by the reaction of polyisocyanate and polyol,
It may be in the form of a urethane resin or prepolymer containing free isocyanate groups and/or hydroxyl groups, or it may be in the form of a urethane elastomer that does not contain these reactive end groups.

Further, usable chain extenders may be the polyhydric alcohols exemplified above (which may or may not have a cyclic hydrocarbon residue in the molecule).

In addition, if a phenoxy resin and/or vinyl chloride copolymer is also included as a binder resin in addition to the above-mentioned urethane resin, the dispersibility of the magnetic powder will be improved when applied to the magnetic layer, and its mechanical strength will be increased. do. However, if only the phenoxy resin and/or the vinyl chloride copolymer is used, the layer becomes too hard, but this can be prevented by containing polyurethane, and the adhesion to the support or base layer is improved.

The phenoxy resin that can be used is a polymer obtained by polymerizing bisphenol A and epichlorohydrin, and is expressed by the following general formula.

(However, nτ82-13) For example, PKHC manufactured by Union Carbide.

There are PKHH, PKHT, etc.

Further, as the above-mentioned vinyl chloride copolymers that can be used, there are those represented by the general formula: In this case, the molar ratio derived from l and m in is between 95 and 50 mol% for the former unit/) and between 5 and 50 mol% for the latter unit. In addition, X represents a monomer residue that can be copolymerized with vinyl chloride, and is a monomer residue selected from the group consisting of vinyl acetate, vinyl alcohol, maleic anhydride, etc. The degree of polymerization is preferably from 100 to 600. If the degree of polymerization is less than 100, the magnetic layer etc. tends to become sticky, and if it exceeds 600, the dispersibility becomes poor. It may be hydrolyzed to

As the vinyl chloride copolymer, preferably vinyl chloride-
Examples include copolymers containing vinyl acetate (hereinafter referred to as "vinyl chloride-vinyl acetate copolymers"). Examples of vinyl chloride-vinyl acetate copolymers include vinyl chloride-vinyl acetate-vinyl alcohol, vinyl chloride-vinyl acetate-maleic anhydride copolymers, and vinyl chloride-vinyl acetate copolymers. Among these, partially hydrolyzed copolymers are preferred. Specific examples of the above-mentioned vinyl chloride-vinyl acetate copolymers include rVAGHJ, rVYHHJ, and rVMcHJ manufactured by Union Carbide, and "S-LEC A" and "S-LEK A-5" manufactured by Building Block Chemical.
, "S-LEC °C", "S-LEC M", "Denkabinir 1000 G J", "Denkabinir 100OWJ" manufactured by Denki Kagaku Kogyo ■, etc. can be used.

In addition to the above, cellulose resins can also be used as binder resins, including cellulose ether,
Cellulose inorganic acid esters, cellulose organic acid esters, etc. can be used. As the cellulose ether, methyl cellulose, ethyl cellulose, etc. can be used. As the cellulose inorganic acid ester, nitrocellulose, cellulose sulfate, cellulose phosphate, etc. can be used. Furthermore, as the 11M ester with ululose, acetyl cellulose, propionyl cellulose, butyryl cellulose, etc. can be used. Among these cellulose resins, nitrocellulose is preferred.

In addition, regarding the entire binder composition, the ratio of the above-mentioned urethane resin to other resins (total amount of phenoxy resin, vinyl chloride copolymer, etc.) is 90/1 by weight.
Desirably 0 to 40/60, 85/15 to 45
155 has been found to be even more desirable. If the amount of urethane resin is outside this range, dispersion tends to be poor.
Also, if there is a large amount of other resins, surface properties tend to be poor.
In particular, when the concentration exceeds 60%, the physical properties of the coating film become less favorable overall. In the case of vinyl chloride-vinyl acetate,
It can be mixed with the urethane resin with a considerable degree of freedom, and preferably the urethane resin is 15 to 75% by weight.

In addition to the binder resins mentioned above, thermoplastic resins, thermosetting resins, reactive resins, and electron beam curable resins may be used as binder resins for the layers constituting the magnetic recording medium of the present invention.

The thermoplastic resin has a softening temperature of 150°C or less, an average molecular weight of 10,000 to 200,000, and a degree of polymerization of about 200 to 2,000, such as acrylic ester-acrylonitrile copolymer, acrylic acid Ester-vinylidene chloride copolymers, acrylic ester-styrene copolymers, etc. are used.

The thermosetting resin or reactive resin has a molecular weight of 200,000 or less in the state of a coating liquid, and after coating and drying, the molecular weight becomes infinite due to reactions such as condensation and addition. Moreover, among these resins, those which do not soften or melt before the resin is thermally decomposed are preferable. Specifically, for example, phenol resin, epoxy resin, urea resin,
These include melamine resin, alkyd resin, etc.

Examples of electron beam irradiation-curable resins include unsaturated prepolymers,
Examples include maleic anhydride type, urethane acrylic type, and polyester acrylic type.

In the magnetic recording medium of the present invention, carbon black may be further added to the layer containing the urethane resin. It is desirable that this carbon black has electrical conductivity, but carbon black with light-shielding properties may also be added. Examples of such conductive carbon blanks include Conductex 97 manufactured by Columbia Carbon Co., Ltd.
5 (specific surface area 250 rrf/g.

particle size 24 μm), Conductex 900 (specific surface area 1
25rd/g, particle size 27 μm), Cabot Vulcan X C-72 (specific surface area 254 td/g, particle size 30 μm), Raven 1
040.420, #44 manufactured by Mitsubishi Kasei ■, etc. As the light-shielding carbon black, for example, Raben 2000 manufactured by Columbia Carbon Co., Ltd. (specific surface area 190 resistance/g,
Particle size 18 μm), 2100.1170.1000, #100, #75, #40, #35, # manufactured by Mitsubishi Kasei ■
30 etc. can be used. It is desirable for carbon black to have an oil absorption of 90 ml (D B P )/100 g or more because it easily forms a stracture structure and exhibits higher conductivity.

The magnetic recording medium of the present invention, for example, as shown in FIG.
A magnetic layer 12 is provided on a support 11 . Also, magnetic layer 1
An 80-layer 13 is provided on the opposite side from the 80-layer 13. Although this BC layer may be provided, it is not necessary to provide it. The magnetic powder used in the magnetic layer 12, especially the ferromagnetic powder, includes:
γ-Fez03, Co-containing r-Fez03% Fe
,, Oa, Co-containing iron oxide magnetic powder such as Fe, 04; F
e, Ni S00% Fe-Ni-Co alloy, Fe
-Mn-Zn alloy, Fe -Ni -Zn alloy, Fe
-Co-Ni-Cr alloy, Fe-Co-Ni-P
Examples include various ferromagnetic powders such as alloys, Co--Ni alloys, and metal magnetic powders containing Fe%NiCo as a main component. Among these, Co-containing iron oxide and metal magnetic powder are preferable. Further, when the BET value of the magnetic powder is 25 nf/g or more, and furthermore 30 m/g or more, the effect of adding the compound of the present invention is remarkable.

The magnetic layer 12 also contains lubricants such as silicone oil, graphite, molybdenum disulfide, tungsten disulfide, monobasic fatty acids having 12 to 20 carbon atoms (such as stearic acid), and monobasic fatty acids having 13 to 26 carbon atoms. A fatty acid ester consisting of a monohydric alcohol, etc.), an abrasive (for example, fused alumina), an antistatic agent (for example, graphite), etc. may be added.

The non-magnetic powder contained in the 80 layer 13 includes carbon black, silicon oxide, titanium oxide, aluminum oxide, chromium oxide, silicon carbide, calcium carbide, zinc oxide, α-Fe*Os, talc, kaolin, calcium sulfate, Examples include those made of boron nitride, zinc fluoride, molybdenum dioxide, calcium carbonate, etc., preferably carbon black (especially conductive carbon black) and/or titanium oxide.

Further, as the non-magnetic powder, organic powder such as benzoguanamine resin, melamine resin, phthalocyanine pigment, etc. may be added.

The magnetic recording medium in FIG. 6 also includes a magnetic layer 12 and a support 1.
1 may be provided with an undercoat layer (not shown), or may not be provided with an undercoat layer (the same applies hereinafter).
. Further, the support may be subjected to corona discharge treatment.

Further, BCN13 may also contain the urethane resin according to the present invention.

In addition, the material of the support body 11 may be plastics such as polyethylene terephthalate or polypropylene, AI, Z
metals such as n, glass, B N s Si carbide,
Ceramics such as porcelain and pottery are used.

In addition, when coating and forming the above-mentioned magnetic layer, etc., it is desirable to add a predetermined amount of polyfunctional isocyanate as a crosslinking agent to the coating material. Examples of such crosslinking agents include, in addition to the polyfunctional polyisocyanates mentioned above, triphenylmethane triisocyanate, tris-(p-isocyanate phenyl) thiophosphite, polymethylene polyphenylisocyanate, etc.; Diisocyanate type is preferable.

FIG. 8 shows another magnetic recording medium.
A 00 layer 14 is provided on the magnetic layer 12 of the illustrated medium. This 00 layer 14 is provided to protect the magnetic layer 12 from damage, etc., and for this purpose, it needs to have sufficient slipperiness. Therefore, as the binder resin for 00 layer 14,
The urethane resin used in the magnetic layer 12 described above is used (preferably in combination with a phenoxy resin and/or a vinyl chloride copolymer). The surface roughness of the 00 layer 14 is Ra≦0.01 μm, Rmax≦0, especially in relation to color S/N.
．． The thickness is preferably 13 μm. In this case, the surface roughness of the support 11 is Rp≦0.01μm, Rmax≦0.13μm.
m, and it is desirable to use a smooth support 11.

FIG. 9 shows a magnetic recording medium configured as a magnetic disk, with magnetic layers 12 similar to those described above on both sides of a support 11.
Each of the 00 layers 14 is provided, and each of the 00 layers 14 may contain a binder resin containing the above-mentioned urethane resin as a main component.

E, Example Hereinafter, the present invention will be explained with reference to specific examples.

The components, proportions, order of operations, etc. shown below may be changed in various ways without departing from the spirit of the invention.

After dispersing the ingredients shown in Table 1, apply 1μ of this magnetic paint.
After filtration with an M filter, 5 parts of polyfunctional isocyanate was added, coated on a support to a thickness of 5 μm, supercalendered, slit to a width of 172 inches, and videotape (each example, comparative 1) handle)
And so. However, the numbers after No. 241jl in Table 2-1 represent parts by weight, and "fruit" from the second column onwards refers to Examples.
Ratio J represents a comparative example. 590 parts of diethyl carbonate and 650 parts of 1,6-hexanediol were heated at 120°C to 20°C.
The reaction was carried out at 0° C. for 15 hours, and then cooled to 150° C., and residual ethanol and unreacted diol were sufficiently distilled off under reduced pressure at 20 to 50 mn+Hg to obtain 770 parts of polycarbonate polyol. The hydroxyl value of this polyol is approximately 6
6 (molecular weight approximately 1700).

Synthesis of polycarbonate polyol polyurethane> (Synthesis Example 1) 170 parts of the polycarbonate polyol synthesized above and 25 parts of diphenylmethane diisocyanate (MDI) were dissolved in 580 parts of methyl ethyl ketone, and 0.03 part of dibutyltinsilaurylate was added as a urethanization catalyst. The mixture was reacted at 80°C for 6 hours to obtain 770 parts of a methyl ethyl ketone solution of polycarbonate polyol polyurethane (solid content 25.0%, 1 layer of polyurethane).
40,000).

(Synthesis Example 2) 162 parts of the polycarbonate polyol synthesized above and 25 parts of MDI were dissolved in 560 parts of methyl ethyl ketone,
Dibutyltinsilaurylate 0.0% as a urethanization catalyst.
03 parts was added, reacted at 80°C for 4 hours, and further added 1.3 parts.
- Add 0.45 parts of butanediol and bring to 80°C for 2 hours.
to obtain 740 parts of a methyl ethyl ketone solution of polycarbonate polyol polyurethane (solid content concentration 2
5.4%, polyurethane Mw 130,000).

(Synthesis Example 3) 153 parts of the polycarbonate polyol synthesized above, 25 parts of MDI, and 1.1 parts of neopentyl glycol were dissolved in 540 parts of methyl ethyl ketone, and 0.03 parts of dibutyltin dilauryl was added as a urethanization catalyst.
The reaction was carried out at 80° C. for 6 hours to obtain 4,715 parts of a solution of polycarbonate polyol polyurethane in methyl ethyl ketone (solid content concentration 24.8%, weight of polyurethane 95,000 yen).

(Synthesis Example 4) 153 parts of the polycarbonate polyol synthesized above, 125 parts of M, and 1.2 parts of trimethanol propane were dissolved in 540 parts of methyl ethyl ketone, and 0.03 part of dibutyltinsilaurylate was added as a urethanization catalyst.
The reaction was carried out at 80° C. for 6 hours to obtain 714 parts of a solution of polycarbonate polyol polyurethane in methyl ethyl ketone (solid concentration 25.0%, 100,000 particles of polyurethane).

(Synthesis Example 5) 236 parts of diethyl carbonate and 520 parts of 1,6-hexanediol were reacted at 120°C to 200°C for 15 hours, then cooled to 150°C, and heated for 20 to 50 m under reduced pressure.
The remaining ethanol and unreacted diol were sufficiently distilled off at mHg to obtain 520 parts of polycarbonate polyol. The hydroxyl value of this polyol was approximately 426 (molecular weight approximately 263). 155 parts of 1,6-hexanediol and 600 parts of 1,10-decanedicarboxylic acid were added to this polyol, and reacted at about 200 to 220°C for 8 hours, followed by a reduced pressure reaction at 30 to 5 QmmHg, and finally 1
150 parts of polycarbonate polyol were obtained. This polycarbonate polyol had a molecular weight of about 1,700 and a hydroxyl value of about 68.

150 parts of this polyol, 25 parts of hydrogenated MDI, and 0.5 parts of neopentyl glycol were added to 52 parts of methyl nityl ketone.
The reaction was carried out in 0 parts at 80° C. for about 6 hours to obtain a solution of Bolligerponate polyurethane in methyl ethyl ketone (solid content concentration 28%).

The polystyrene equivalent molecular weight V layer of the same polyurethane was determined by GPC to be 110,000.

(Left below) Mixtures of monoesters and diesters of H and phosphoric acid The following measurements were made on the videotapes from each side described above.

Chroma S/N: Color Video Noise Meter
Measured using 925D/IJ.

Rumi S/N: Same as above.

RF output at 4MHz using a VTR deck for measuring RF output.
The output was measured, and after 100 playbacks, it showed a value that was lower than the initial output.

(Unit: dB) Still image lifespan: Indicates the time in minutes until the still image deteriorates by 2 dB. The larger the value, the higher the durability and wear resistance of the magnetic recording medium.

The performance of each example videotape is shown in Table 2.

(The following is a margin) However, for Real-1 and Real-2, the chroma S/N, lumi S/N, and RF output were determined using the value of ratio -1 as OdB.

For actual-3, the chroma S/N, lumi S/N, and RF output were determined using the value of ratio-2 as OdB.

The above results show that the tape performance is significantly improved by adding the compound of the present invention and the urethane resin to the magnetic layer according to the present invention.

[Brief explanation of drawings]

The drawings show embodiments of the present invention, and FIG.
A graph showing the change in the amount of powder falling off depending on the number of carbon atoms in the diol. Figure 2 is a graph showing the change in the amount of falling powder depending on the average molecular weight of polycarbonate polyol. Figure 3 shows the still durability depending on the proportion of polycarbonate polyol. Graph, Figure 4 is a graph showing the still durability according to the average molecular weight of polycarbonate-based polyurethane, Figure 5 is a graph showing the dispersibility according to the average molecular weight of polycarbonate-based polyurethane, Figures 6, 8, and 9. 7 is an enlarged sectional view of a portion of the magnetic recording medium from each side, and FIG. 7 is a curve diagram showing the relationship between the stress elongation rate of the urethane resin. In addition, in the symbols used in the drawings, 12...
-------------Magnetic layer 13----------1 Back coat layer (BC layer) 14---------Overcoat layer (0
0 layer).

Claims (1)

[Scope of Claims] 1. A magnetic recording medium in which a magnetic layer contains polycarbonate polyurethane and a compound represented by the following general formula. General formula: ▲There are mathematical formulas, chemical formulas, tables, etc.▼ {However, A is a hydroxyl group or a group represented by -OM (M is an alkali metal), or ▲There are mathematical formulas, chemical formulas, tables, etc.▼
The group represented by n is a real number of 1 to 30. }